This research is concerned with the interplay of cardiac and pulmonary performance. It includes two different, but interrelated components: the control of breathin in animals and man and the control of the pulmonary circulation. Each of these categories has individual subsets. With respect to the control of breathin, one group of investigations is dealing with the respiratory centers in the brain; a second group with the flow of information to the brain that determines the rate and patterns of breathing. To complete this approach, the research includes ultrastructural aproaches to the anatomical bases for breathing and a comparison of mammalian mechanisms with those of primitive forms in which many of the sophisticated overlays of animals and man are lacking. The control of the pulmonary circulation focuses in several distinct entities. The first is the development of an experimental model of pulmonary hypertension; for this purpose, dietary manipulation and the heart worm of the dog are being used. The second is pulmonary edema from the point of view of structural functional interplay at an ultrastructural level. The third is the performance of the right ventricle when subjected to the load of pulmonary hypertension.